400 REPORT— 1894. 



turned off, and the tank contained exactly one hundredweight of con- 

 densed steam. The condensing water was then stirred and the tem- 

 perature taken. The thermometers were sensitive (1° C. corresponded to 

 1 in. in some of them), and they were carefully compared with standai'd 

 thermometers. A very small radiation correction was made. The ^-alue 

 of the dryness fraction found on different days was •9996, '9638, -9949, 

 •9646, -9976, -9893, 1^0072, 1^0048, -9987. The mean of all is 0^991 1, 

 showing an average of about 1 per cent, of moisture in the steam. In 

 spite of the large scale on which the experiment was tried and the care 

 taken, the results are rather discrepant, and two of them give values 

 which it would seem must be erroneous. 



IV. Continuous Condensing Method.- — -The difficulties of the ordinary 

 condensing method have led Mr. Barrus, Mr. Hoadley, and other ob- 

 servers to adopt a process of continuous steady condensation. The steam 

 may be condensed (a) in the condensing water, or (^) in a surface con- 

 denser. The first method ' may be carried out by the apparatus shown 

 in fig. 3. Steam passes from the steam pipe, S, to a small injector, /. 

 The condensing water is drawn from the tank A, and the mixed water 

 and condensed steam are discharged into the tank B. If W, is the 

 decrease of weight of A in any interval, and Wo the increase of weight 

 of B, then w=W2 — W, is the weight of steam condensed. Thermo- 

 meters t, t, give the temperatures of the water entering, and mixed steam 

 and water leaving the injector. Let <,, t^ be these temperatures, and t 

 the temperature of the steam. Then, if x is the dryness fraction, 



w{{t-t^) + :,<L] =W,(^2-'i) 



W 



1 {t^-t^) + t,-t 





~ (t2-t,) + t2-t 



1116-0-71(1 



Mr. Barrus has used a surface condenser (fig. 4), consisting merely of a 

 short vertical pipe in a vessel through which cooling water circulates. The 

 condenser is supplied with cooling water at a fixed rate of flow. Then, as 

 the condensing surface is constant, the rate of condensation is constant, 

 and the rise of temperature of the cooling water is constant. Condensation 

 is carried on for any convenient period, and the condensed steam run off' 

 for weighing. Simultaneously a series of readings are taken of the 

 temperature of the water entering and lea\'ing the condenser, and of the 

 condensed steam. The radiation correction can be determined by observing 

 the fall of temperature in the condenser when the supply of steam and 

 cooling water is stopped.^ The continuous condensing method seems likely 

 to be more accurate than the ordinary method, but the arrangements ai^e 

 more complicated. 



V. Method by Superheating. — Mr. G. H. Barrus about 1890 devised a 

 calorimeter in which the steam to be tested passed through a chamber 

 jacketed with superheated steam. The steam was thus dried and super- 



' Carppnter, Experimental Engineennj, p. 375. 



^ See Peabody, Thermodynamics of the Steam Engine, p. 232 ; Carpenter, E.vperi- 

 mental Engineering, p. 380. 



